Cable



June 3, 1930. yE, KAEMPF ET AL 1,761,565

CABLE Filed May 25, 1929 C Ig mi@ H ,n

F/GZ

E. KAEMPF D P DALzELL BY @JM i EMIL KAEMPF AND DONALD IE. DALZELL, OFALDWYCH, LONDON, ENGLAND, ASSIGN' electrical circuit causing electricalinfluences Patented June 3, i930 lUNrri-:D STATES 4ParamaroFFlcE ORS`TOWESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A

CORPORATION OF NEW 'YORK CABLE Application led May 25, 1929, Serial No.365,846, and in Great Britain May 22, 1928.

consisting of more than one circuit diiliculties are encountered owingto mutual interference between the various circuits.

This interference is due to inequalities in the electrical properties ofthe two sides of one which unequally affect the two sides ofl anotherelectric circuit.

These inequalities are due to defects in manufacture 'and raw materialsand to the fact that the two sides of a circuit vare necessarilydistinct and are, therefore, not general-V the same or different typesare assembled and then included in layers consisting each of helicallyapplied stranding units of the same type or of different types to make acable core. One or more cable cores may compose a cableunit.

The present invention concerns a cable in which such interferencesapproach a minimum and consists in a cable in which the interferencebetween circuits in the .cable due to differences in the relation of twosides of a circuit to another circuit or to the regular v and repeatedrecurrence of such differences may be largely avoided by the use of adefinitesystem or systems of twisting and stranding.

lar insulated conductors. The term strand- For simplicity of expositionthe definitions as herein understood are given for a single cable corecontaining several layers each composed of pair circuits consisting oftwo simiing torsion of each of the several layers is given to the numberof revolutions, whether right or left, and fractions of a revolutionywhether right or left severally and simultaneously executed by thoselayers in unit.

length of the cable core, measured axially along the core. The termtwisting torsion of any one pair is given to the expression obtained bymeasuring the axial length of core between two successive appearances onthe outside of its own layer of one and the same wire of that pair andtaking the reciprocal of the number expressing this distance. This axiallength is also called the -twist length or length of twist. ln bothdefinitions the same method and units of length measurement areemployed.

The deiinition 4oit' twisting torsion may be suitably modified to applyto circuits contained in stranding units consisting of more than twowires, such, for example, as a quad.

The twisting torsion of one palr of a quad.

about another pair of the quad is the expression obtained by measuringthe axial length of core between two successive appearances on theoutside of its own layer of one and the same pair of the quad and takingthe reciprocal of the number expressing 'this distance.

ln the case of cables consisting of quadded stranding units manyempirical rules are known and employed for the choice of one or more ofthe torsionsvin a stranding unit when the remaining torsion or torsionsare given or when some relation or relations betweenthe several torsionsare given or inv some similar sets of circumstances. Any such rules mayreduce interference between the several cireults of a strandmg unit, butis ineii'ective in the reduction of interference between circuits ofdifferent stranding units. The use, however, of dissimilar strandingunits, (e. g. units of dilferent twisting torsions) in a pair ofstranding units adjacent in the same layer or the use of dissimilarstranding units for a pair of stranding units, one of which is in thelayer adjacent to that with given stranding torsions and inthe case Y ofquadded cable a certain system of pair torsions is used with given quadtorsions.

The -drawing gives diagrams used to explain the invention.

Fig. 1 is a diagram of two dpairs of conductors in a cable having stran'ng units (in this case, pairs) applied in layers, the lay beingopposite in the adjacent layers Fig. 2 showsa plot ofthe equation or,

rather, set of equations, n1i1i2-=2N which equation is derivedhereinafter, with indications of preferred and other suitable speciiictorsions (defined hereinafter), and in- ,dications of permissiblemanufacturing variations; and

Fig. 3 is a diagram useful f or explaining the preferred relation of thetwisting torsions of pairs in two quads to the twisting torsions of theuads themselves.

In Fig. 1 the conductors aand b form a paire, b, and the conductors cand d form a air c, d. The conductors of pair a, l), which ie in one'layer are twisted together .with a twist length L1 measured -axially ofthe cable, whilst the conductors of aire, d, lie in an adjacent layerand are twisted'together with a twist length L2. A twist length is theaxial length of a lcomplete twist of the conductors about one another.It is convenient to refer to the twisting torsion of a pair hereinbeforeThe twisted pairs are stranded into the cable and the strandiiig of thepairs, a, and c, (l, are in the directions e and f respectively. In thepositionshown in Fig. 1 the pairs a, I), and c, d, present a certainmutual aspect and this precise aspect will recur at other parts of thecable when the pairs occupy a precisely similar relative position. Itmay be convenient in practice to use the saine stranding lay definedasl-1J' as the pair torsion t- S for the two layers ,containing a, b,and c, d,

and under such conditions the pairs a, b, and c, d, will occupy similarrelative positions (except as regards the pair twists) on the other sideof the cable at an axial distance 2 from the position shown.

They position of the line joining the centers of the pair of conductorsa, and b with respect to the line joining the center of that line to thecenter of the cable, i. e., a radius R, may be represented by the angle6,. Similarly 02 represents a similar angle dependent in magnitude uponthe position of conduc- Mamet tors in the pair c, d. We may term thedifi the other side ofthe cable at an axial dis-l tance from the firstposition at which the pairs are together the angular disposition of theconductors aand'b may be represented by tig +01 and (if/2g +02) and therelative angular disposition is The significance of the angular valuessuch as 4 and qbl will be more readily perceived if they are consideredas numbers representing proper or improper fractions of revolutions.

he repetition of the relative spacial position of the pairs shown inFig. 1 will occur when 1=N whereN is a whole number, and'therefore whent, g ttf-g2- =N, any integer.

If we term S the specific pair torsion (n) i. e. the ratio of thetorsion of a pair to the stranding` torsion we may express the criticalconditions to be avoided as rainy-22W This equation when plotted givesthe family of straight lines illustrated in Fig. 2. By choosing pointswhich lie most remote from these lines ideal twists maybe chosen for thepairs, so that a minimumof disturbance is` produced, for `example asuitable choice of twists for a, b, and c, d, would be n1=1, 3, 5,7,etc. and 712=2, 4, 6, 8, etc. These give ideal conditions but inpractice it may not always be convenient to use them and perfectlysatisfactory results can be obtained by using values Within thefollowing limits, for example n1=1i1/2, 3i1/2, 5tlg/2, and a2=2i1/2,Litl/2, Gil/2, etc. or expressed in words the specific torsions of .thepairs in one layer must differ from some one of the numbers 2n where nis an integral number by less than 1/2 and the specific torsions of thepairs in an adjacent layer must differ from somel one of the numbers2n+1 Where n is an integral number by less than 1/2.

Intlie above example we have taken the stranding torsion to be the samefor layers containing both units a, b, and c, d. If differentstrandingtorsions are used the above principle of determining suitable torsionsremains unchanged except that for the stranding torsion the mean valueof the two is taken.

In Fig. 2 we have shown how points lying at the centre of the squaregive ideal choice and'represent the torsions which give minimum ofinterference. These torsions may be termed ruthless torsione since theygive an absolute minimum of interference, disregarding extraneousiniluences. Other choices which give reasonable values'offinterferenceare also apparent. Thus, W, X, Y Z repre- A sent ruthless toi-sions,whilst, S, T, V, give another quite suitable choice, O, P,- Q, R, isanother satisfactory relationship of torsions and AI, J, K, L, M, N,belong to a set of torsions giving a reasonably small value of in-lterference. In all cases the points representing the chosen torsions lieremote from this invention not only is the inter erencey between quadsin adjacent layers reduced to a minimum, but also the interferencebetween adgacent quads in the same layer 1s to a yconsiderable extentreduced.

ln order to reduce phantom to pair uni balance in adjacent quads of alayer, the

principle above derived may be further developed. ln Fig. 3, A and Brepresent adjacent quads of a layer in a cable, quad A comprises pairsa, and quad B comprises pairs c, d. lt is necessary to determine asuitable relation between` the quad twist (twist ot one pair about theother pair) of l., the pair twist (twist of one conductor about theother) of d' and the quad twist of A.

More particularly, referring to Fig. 3, a represents a twisted pair, banother twisted pair and the pairs a and are twisted together inaccordance with a quad twist to form a quad. Pair cis also twistedtogether, pair d is twisted together and pairs c and d are given a quadtwist to form a quad. Pair a, constitutes a circuit, pair constitutes acircuit, pair c constitutes a circuit and pair d constitutes a circuit.Pairs a and I) together form a phantom circuit and pairs c and d aphantom circuit. ln considering the intertering eiect of the phantomcircuit of quad A upon the circuit of pair d the pair twists of themembers of pairs a and about each other may be neglected and theirtwisting progression according to the quad twist only need beconsidered. In other words, the pair a may be considered as oneconductor represented by'a circle in the diagram and the pair t anotherconductor represented by another circle. These pairs and hence theconductors which they represent, twist about each other with a quadtwist in accordance with well known methods Aof lconstruction. Inconsidering the eilect of the phantom circuit of quad A upon the circuitof pair d we have three angular progressions to consider and these areanalo ous to the progressions jnvolved in' twister? pairs lying inadjacent layers.. The analogies are as follows The angular progressionof the pair twist of one of the twisted pairs in a layer (Fig. 1)corresponds to the angular progression of the pair twist of the pair din a quad (Fig. 3) the angular progression of the pair twist oi' 'atwisted pau` in an adjacent layer (Fig. l) corresponds to the angularprogression of the quad twist of an adjacent quad suchas A (Fig. 3) andthe relative angular progressions of the stranding lays of the two pairs`in adjacent layers (Fig. l) corresponds to the angular progression ofthe quad twistl of the quad including the pair such as quad B (Fig. 3).;Since the situations are analogous, similar equations may be used. Thusif We take the equation tgg N and `isubstitute -l-IJS for 15 for t2, andT for S we get T T E i :i IV,

in which is the reciprocal of the axial 3 length of a complete twist ofthe pair d; is the reciprocal of the axial length of a complete twist ofquad A, and 'l is the axial length of a complete twist ot quad B. rlheseand E;

reciprocals of a twist length, l152 and Ll are likewise reciprocals of atwist length, and 'l substitutions are validbecause 151 are and areaxial lengths in which interfering members repeat their nearest approachto one another. Tis used instead of E because, whereasin the case oftwisted' pairs in adJacent layers, the pairs approach each -other twicein a complete strand about the are not notably detrimental for values ofN except When il. Consequently N may llU yof the quad torsion of thatquad yand the (luces to l l 1 1 is the torsion of a pair of one quad, 3

L isthe quad torsion of an adjacent quad,

and is the quad torsion of the quad including the pair.

Expressing the implication of the equation in words, the pair torsion ofa pair should approach neither the sum nor the difference of the quadtorsions of a quad containing that pair and an adjacent quad. If theapproach does not fall between 4/5 and 6/5 of the sum or the difference,the interference between the pair in one quad and the phantom circuit inan adjacent quad is not unduly large. i

As hereinbefore defined, a stranding unit comprises one pair or amultiple of pairs twisted together be ore being stranded upon the cable.l

What is claimed is:

1. A cablell comprising stranding units contained in akljacent layers ineach of which are at least two dissimilar stranding units, the specifictorsion of each of the two units in one layer differing from one of thenumbers, 2n, by less than lone-half, and the specific torsion of each ofthe two units in the other y the torsion of a pair 1n one quad 1s notbe- L2=the length of twistof the unit fering therewith N is an integralnumber.

5. A cable comprising conductors arranged' in stranding unitswhichinclude pairs in which a substantial majority of the pairs have twistingtorsions such that the recurrences of the identicalpair relativeposition of any particularvpair to a. stranding unit adjacent to it atany particular cross-section are reduced by choosing twisting torsionswhich l i i avoid the condltions T- 4 -L3=1=L where T is the length oftwist of a stranding unit ininter-- In witnesswhereof, I hereuntosubscribe tween 4/5 and 6/5 of the sum ordifference y quad torsion of anadjacent quad.

3. A cable according to claim 1 in which some of the stranding units arequads and the quad and pair torsions of a substantial majority ofadjacent quads are such that the torsion of a pair in one quad does notfall between 4/5 and 6/5 of the sum of the quad' torsions of that quadand an adjacent quad.

4. A cable comprising conductors arranged in stranding units containedin layers in each of which are at least two dissimilar stranding units,characterized in this, that a substantial majority ofthe units inadjacent layers, have twisting torsions reducing the recurrence of theprecise relative special position of two mutually interfering units aspresented at any particular cross-section by choosing twisting torsionswhich avoid the conditions where S is the common or mean stranding lay,

L1=the length of twist of one unit

